Wind turbine generators, in which a wind turbine is rotated by the force of wind and rotational movement thereof is transferred to a generator to generate electricity, are conventionally provided with a yaw system which revolves (turns) a nacelle depending on the wind direction.
The conventional yaw system includes a yaw drive device, a yaw slewing ring, and a yaw brake. Main components are disposed in the nacelle. Specifically, the nacelle, which includes the wind turbine and a powertrain that generates electricity by using the force of rotation of the wind turbine, is revolved at the top of a tower by the operation of the yaw system, and is pointed in the optimum direction for generating electricity depending on the wind direction.
In a conventional yaw system 10 shown in FIG. 8, a nacelle 3 is revolvably attached to a tower 2, which is a fixed side, via a yaw slewing ring 11 which uses a plain bearing 20 serving also as a yaw brake. In FIG. 8, reference numeral 12 indicates a nacelle base plate constituting the nacelle 3. A yaw drive device 15 which includes a electric motor 13 and a drive gear 14 is fixedly provided on the nacelle base plate 12.
The plain bearing 20 includes a fixed seat 21 which is fixed to a flange part 2a of the tower 2 and a bracket 23 which holds brake pads 22. The bracket 23 used in this case is a member having an approximately L-shaped cross-section. The upper end face of the bracket 23 is fixed to the lower face of the nacelle base plate 12.
In the plain bearing 20 having this structure, the brake pads 22 slidably support the upper and lower faces and the outer circumferential face of a rim part 21a provided on the fixed seat 21.
In this case, reference symbol CL indicates the axis center line of the tower 2 in FIG. 8. Thus, the yaw drive device 15 is disposed outside the tower 2 in this configuration example.
In the yaw drive device 15, the drive gear 14 is engaged with a ring gear 16, which is a fixed side, so that the nacelle (the nacelle base plate 12, the bracket 23, etc.), which is a movable side, can be revolved together with the drive gear 14 in response to the rotation of the electric motor 13 (for example, see Patent Document 1).
Patent Document 1:    Japanese Unexamined Patent Application, Publication No. 2007-51585